FAB system for defining AML

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Dear OncoLink "Ask The Experts," Can you please tell me what M4 (FAB) means with AML? Is that type treated different or hard to treat? I am a little confused. Is one sub-type worse than the other?

Selina M. Luger, MD, Director of the Leukemia Program and Assistant Professor of Medicine at the University of Pennsylvania, responds:

In the 1980's a group of French, American and British physicians (FAB) came up with system for defining or naming the different forms of AML (acute myelogenous leukemia) They named them based on the way they looked and tests that would help to define the type of cell that had become the leukemic cell. Since that time we have learned that although these nametags help us identify the leukemia, for the most part they don't mean much in terms of how the leukemia is going to behave or how the patient is going to do. We now know that there are other factors about the patient (like their general health, age etc), and the leukemia (whether it came out of nowhere or because of other treatments or diseases the patient has) and the cells (what the genes or chromosomes of the leukemia cells look like) that are more important in predicting how a patient might do. We still do however use the FAB nomenclature to give the leukemia a name.